DESCRIPTION: The long-term objectives of the investigator's research program are to investigate relationships between caffeine and stress reactivity and to determine their implications for health and disease. The proposed study seeks to investigate caffeine's effects on cardiovascular and neuroendocrine stress responses in the natural environment. Ambulatory blood pressure and heart rate as well as catecholamine and cortisol excretion will be collected during normal workday activities, in the evening, and overnight to measure the magnitude of physiological stress responses. Daily caffeine dose will be experimentally manipulated within-subject in a cross-over design to determine whether higher daily caffeine doses produce increased physiological stress responses and greater subjective experience of stress during the workday in men and women who drink coffee. Comparisons of workday and evening measures will determine if caffeine inhibits "unwinding" at home after the day's activities. The investigators will also study two groups who may be at greater risk from the effects of caffeine: women who use birth control pills, and cigarette smokers. In the entire sample, job strain, cynical hostility, and measures of stress at home will be studied as potential moderators of caffeine/stress interactions.